This invention relates to automatic feeding apparatus for transferring work pieces to a work station.
In the operation of presses, the transfer of blank stock or work pieces from a supply point to the collect for holding the work piece has been for years accomplished by a manual transfer. The speed of operation of the press was thereby limited by the manual dexterity and speed of the operator placing and removing the work pieces from the press. In addition, the requirement for an operator to be in attendance at each press meant a significant labor expense attendant upon the operation of the press.
In addition to the limited speed of operation and the labor involved, the manual operation of such a press also invariably involved a safety factor. An operator transferring work pieces to and from the collect at the work station was required to physically grasp the work pieces and coordinate the operating cycle of the press with his manual movements such that there was a smooth flow of work pieces to and from the work station. Operators of machine tools of this type, despite efforts to observe safety practices, were inevitably faced with situations in which the operator reached into the work area of the press during its operation and on occasion experienced injuries when their hands, arms, or articles of clothing were caught or entangled in the press. In addition, the manual operation of such a press or other type of machinery was typically quite monotonous, tending to lull the operator and tire him quickly. In such an event, the efficiency of the operation of the press declined and safe operation was significantly reduced.
To remedy the foregoing, automatic feeding apparatus or industrial robots for transferring large numbers of pairs on a one-by-one basis from a supply position to a work station of a machine tool or press and for removing parts which have been finished at the work station have been utilized. The use of industrial robots for automatically feeding the press allows operation of the press to be continuous and fully automatic without the need or requirement of attendance of an operator thereby enabling one operator to be responsible for and to adequately supervise the operation of a plurality of such presses. The movement of the industrial robot working arm to supply work pieces to the press is electronically synchronized with the press so that the operation of both pieces of apparatus cooperate with each other.
In the typical operation of a press, a die set is chosen for operating on a part of a specific size and for producing cut-outs of a specific configuration. A plurality of blank stock or work pieces are stacked preparatory to feeding the work pieces into the press by the robot. The work pieces are lifted off the stack individually by the pick-up arm of the robot and transferred to the press collet where the work piece is deposited and held during the operation of the press. Upon completion of one full cycle of press operation, the collet releases and the finished part is transferred to storage.
It has been common practice wherein a plurality of metal blank stock or work pieces are stacked to provide for the uppermost work pieces to be levitated as by magnetism. In known devices of this type, the magnets are arranged so as to prevent the work pieces at the top of the stack from sticking together due to the presence of lubricant or burr thereon. The levitating or fanning effect of the blanks is due to the fact that two ferromagnetic bodies such as the work pieces in a magnetic field will repel each other. The use of magnets to levitate the magnetizable work pieces in the stack is disclosed in prior art references such as U.S. Pat. Nos. 1,716,602, 2,847,212, 3,353,822 and 4,024,963.
One of the difficulties in using an industrial robot for transferring work pieces from a stack to the press is that the precise location of the pick-up point of the work piece from the stack by the robot arm varies as the height of the stack changes. When the work piece is placed in the press, it is necessary that it be placed in the press always at the exact desired position therefore the pick-up point of the work piece from the stack must always be exact and not vary.
By this invention, there is provided automatic feeding apparatus for transferring magnetizable work pieces to a work station automatically as by a robot and which provides for the correct pick-up point by the robot of the work piece and its subsequent disposition in the press.